During a voice teleconference, it is often desirable for two or more conference participants to be able to both view and discuss common data objects such as a set of images. For example, one participant may desire to conduct a slide presentation concurrent with a voice conversation among the participants. Systems which enable a person to receive and view image data over a telephone line concurrent with voice conversation are known. One such system interrupts the telephone conversation momentarily to allow visual data to be transmitted over the telephone line. Following the transmission of visual data, the voice communication can be automatically resumed. Other known systems for sharing voice and image data generally require relatively complex equipment, specially enhanced modems, or dedicated high speed digital lines such as Integrated Services Digital Network (ISDN). Still other systems require multiple telephone lines to handle both data object manipulation and voice. Generally, the known desktop teleconferencing systems are for point-to-point communications rather than multipoint, multiparty communications.
It would be advantageous to provide a teleconferencing system which avoids having to interrupt voice communication in order to transmit data objects such as images meant to be viewed and discussed concurrently. It would also be advantageous to be able to provide such a teleconferencing capability without requiring complex devices or dedicated lines. The above and other advantages are achieved by the present invention. In general, the teleconferencing provided by the present invention allows multiple users to conduct a voice conference over standard telephone lines while simultaneously viewing shared slides, graphs, text, or other data objects.
The improved teleconferencing system stores a common set of data objects, such as slides, in a digital computer associated with each participant prior to the start of a voice conference. Once a voice conference is underway, a lead speaker can generate audible signals (e.g., Dual Tone Multi-Frequency (DTMF) tones) to which the computers respond to coordinate simultaneous display of the data objects on each participant""s computer screen. Since the data objects are stored prior to the conference and the audible signals are sent with voice communications signals, the voice conversation can flow naturally and uninterrupted by data transmissions.
To facilitate storage and dissemination of the common data objects, a novel arrangement is employed whereby a host computer, preferably configured as a bulletin board system (BBS), serves as a central repository for collecting subsets of data objects from conference participants and combining the subsets into a common set prior to a conference. Participating speakers each initially connect to the host computer and transmit a subset of data objects to the host computer. Participants (speakers and conference attendees) in turn are able to retrieve the common set of data objects from the BBS host computer before entering into a voice conference.
The host computer connects to a central station having a crosspoint switching matrix for interconnecting participants, or users, into multipoint voice conferences. The participants connect to the central station over standard telephone lines. An inexpensive user station controlled by the participant""s digital computer facilitates selection between voice and data modes of access to the central station and the host computer. A participant can generate and receive audible signals via the user station to control conference and switching actions in relation to the user station and the central station. For example, a participant can generate an audible signal which switches the participant""s user station from a voice mode to a data mode and concurrently reconfigures the central station to connect the participant either to the BBS host computer or to another participant for data mode operation.
Accordingly, a voice/data teleconferencing system interconnects a plurality of user sites and a central site over a plurality of communication paths, such as telephone lines. Each user site may include a user digital computer connectable to a user modem for transmitting and receiving data signals. A host digital computer at the central site is connectable to a plurality of host modems for transmitting and receiving data signals to and from the user sites.
A user station located at each user site includes a data port connectable to a user modem, a telephony circuit capable of transmitting and receiving voice communications signals, and a mode selector for alternately connecting the data port and the telephony circuit to a communication path. The mode selector has a data mode position in which the data port is connected to the communication path and a voice mode position in which the telephony circuit is connected to the communication path and the data port is connected to a user modem loopback impedance. The mode selector is responsive to a selector control signal to switch from data mode to voice mode, and the selector defaults to the data mode in the absence of the selector control signal. Thus, in the data mode, data signals can pass between the data port and the communication path, and in the voice mode, voice communications signals can pass between the telephony circuit and the communication path while the user modem is held xe2x80x9coff-hookxe2x80x9d by the loopback impedance. The user digital computer is programmed to control the user station.
The user station further includes a tone generator and tone detector for respectively transmitting and receiving audible conferencing signals with the voice communications signals over the communication path.
A central station at the central site includes a plurality of line ports and a switching matrix for interconnecting the user stations. The switching matrix comprises a plurality of crosspoint switching elements, each switching element actuable to connect one line port to another line port in response to matrix control signals. The central station further includes a plurality of tone generators and tone detectors coupled to respective line ports for transmitting and receiving audible conferencing signals to and from user stations.
The central station further includes a plurality of computer ports connectable to respective host modems. The central station includes central selector means for alternately connecting a line port and a host modem loopback impedance to a respective computer port. The central selector means has a pass-through position in which the line port is connected to the computer port and a loopback position in which the host modem loopback impedance is connected to the computer port. The central selector means responds to central selector control signals to switch from a pass-through position to a loopback position and defaults to the pass-through position in the absence of central selector control signals, such that in the pass-through position, data signals can pass between a line port and a respective computer port.
The central station further includes a controller for controlling conference and switching actions in the central station.
According to another aspect of the invention, each user site can record audible conferencing signals and voice communications signals in a voice conference for playing back at a subsequent time in conjunction with simultaneous display of the data objects on the user computer screen.
The above and other features of the invention including various novel details of construction and combinations of parts will now be more particularly described with reference to the accompanying drawings and pointed out in the claims. It will be understood that the particular teleconferencing system embodying the invention is shown by way of illustration and not as a limitation of the invention. The principles and features of this invention may be employed in varied and numerous embodiments without departing from the scope of the invention.